Web usage, file transfer, multimedia applications, and other popular applications place high demand on data communication networks, calling for strategies to address the bandwidth and error rate demands placed upon channels. Wireless networks have a particularly strong need for communication strategies that address the growing demand for ubiquitous multimedia access. A significant bottleneck in satisfying the increasing demand for content-rich multimedia access is the dynamic error conditions caused by wireless channel variations.
In order to address the above concern, several link and physical layer error control techniques have been proposed that introduce redundancies in transmission to counter the presence of errors. However, due to the redundant data transmission, the physical/link layer techniques may lead to very high communication overhead in terms of the energy consumed and the latency experienced.
A number of adaptation techniques have been proposed to address erroneous transmission in wireless multimedia by using information about specific application object types, such as image and video. One class of techniques is based on Unequal Loss Protection (ULP) framework. In this framework, given a target bandwidth (expressed as the total number of packets), the goal is to protect different parts of the object differently so as to maximize the quality of the data under current channel condition. It is assumed that the channel condition is known a-priori, and is static during the transmission period.
In another class of techniques, called Priority Encoding Transmission (PET), each packet is protected differently at the lower layer using some priority information provided by the higher layer. The advantage of this technique is that it can potentially vary the protection level dynamically as the physical layer channel condition changes. However, such PET techniques do not specify how to optimally assign priorities to different packets based on the changing wireless channel conditions.